Systems Development

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Systems Development

• Infsy 570
• Dr. Ocker

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What we Mean by Software Quality
Software Quality
Effective- ness
Maintain- ability
Usability
Efficiency
Reliability
Understand ability
Modifiability
Testability
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Techniques for Information Gatheringin Systems
Analysis
Information Gathering Techniques
Deriving from the Analysis of the Business Area
Experimenting with the System under Dev.
Asking the Users
Deriving from an Existing System
Interviewing Questionnaires Group Decision-Making
Processes
Data Analysis Document Analysis Observation Partic
ipation
Business Systems Planning Critical Success
Factors Decision Analysis
Throwaway Prototyping Evolutionary Development
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Systems Development Methods

• Systems development - refers to all the
  activities that go into producing an information
  systems solution to an organizational problem or
  opportunity

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Various methods for building information systems

• I. traditional - systems development life cycle
• II. prototyping
• III. application software packages
• IV. outsourcing

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I. systems development life cycle (SDLC)

• oldest method for building systems
• assumes that system has a life cycle with a
  beginning, middle, and end
• structured type of problem solving with distinct
  stages, activities, and deliverables
• each stage consists of activities which must be
  completed before next stage begins

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Systems Development Life Cycle
Tasks
Development Stages
Deliverables
Recommendation to Proceed and System Proposal
or Recommendation to Abandon
Feasibility Study
Systems Analysis
Requirements Analysis
Requirements Specifications
Logical Design
Conceptual Design or Programs and Databases
Systems Design
Detailed Design of System Modules and
Databases Specification of System Hardware and
Software
Physical Design
Coding and Testing
Programming (Construction)
Accepted System with Complete Documentation
Conversion
Installed Operational System
Installation
Postimplemen- tation Review
(System Operation and Maintenance)
Recom. for Enhancement of the System and of the
Dev. Method Recom. for Org. Adjustment
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Systems Analysis

• Determine what the system will do (as opposed to
  how )
• 2 stages
• 1. Feasibility study (preliminary investigation)
• 2. Requirements Analysis

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Feasibility Study

• Objective is to establish whether the proposed
  system is feasible/desirable before resources are
  committed
• systems analyst perform a preliminary
  investigation of the business problem/opportunity
• takes about 5-10 of projects resources (time
  money)

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Feasibility Study Tasks

• Define problem/opportunity
• establish overall objectives of system
• identify users of system
• establish scope of system

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Outcome of Feasibility Study

• Recommendation to proceed or to abandon the
  project

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Requirements Analysis

• Objective is to produce the requirements
  specifications for the system
• details about what the system will do

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Requirements Analysis establishes

• Outputs of system
• inputs to system
• processing steps needed to transform inputs into
  outputs
• files and databases needed to store data

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Requirements Analysis establishes

• The volumes of data to be handled
• numbers of users
• file and database capacities

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Information gathering techniques

• 1. Ask users
• 2. Derive from existing system
• 3. Derive from analysis of business area
• 4. Experimenting (i.e., prototype)

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Systems Design

• details how the system will meet the requirements
  as determined by the systems analysis
• like a blueprint for a house - details all the
  specifications that give the system its form and
  structure

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Systems Design

• Must look at
• Hardware Software
• Program Modules
• Specifications of the modules
• Design the Data base
• Design the USER interface
• Develop the system procedures

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Systems Design

• 2 types of design
• logical
• physical

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Logical Design

• A more macro level design
• conceptual
• activities include
• devising alternative solutions to problem and
  choosing an alternative
• user interface design
• logical/conceptual design of database

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Physical Design

• Objective is
• to produce a complete specification of all system
  modules and of interfaces between them
• to perform the physical design of the database

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Physical Design

• When the physical design is complete, the
  following aspects will be specified
• system outputs (e.g., report layouts, screen
  designs)
• system inputs
• user interface
• platforms (HW, SW)
• program design
• detailed test plan
• database
• conversion plan

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Programming

• programming and documenting code

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Testing

• System pieces and later, the entire system, are
  run for purpose of finding errors

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Conversion

• Plan to move from old system to new system
• parallel - old and new systems run together
• direct - turn off old, turn on new
• phased - convert new system in increments by
  function
• pilot - introduce system to one organizational
  area before proceeding to the remainder of the
  org.

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Post-implementation Review

• evaluating system after it is in production (i.e.
  after installed and in use for awhile)
• post-implementation audit
• Did we do what we said we would do?

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Cyclical nature of SDLC

• when an analyst finishes one phase and proceeds
  to the next, the discovery of a problem may force
  the analyst to go back to the previous phase

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Limitations of SDLC

• appropriate for building large transaction
  processing and management information systems
  where requirements are highly structured and
  well-defined
• also used for complex technical systems (e.g. air
  traffic control) where formal and rigorous
  requirements are needed, along with tight controls

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Drawbacks

• 1. resource intensive - takes lots of time to
  gather detailed information and prepare volumes
  of specifications

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Drawbacks

• 2. approach is inflexible and inhibits change -
• to make changes/ correct errors - repeat
  appropriate life cycle activities, but must
  generate more documents - substantially increase
  development time and costs
• encouraged to freeze system specifications early
  in development process - so changes not encouraged

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Drawbacks

• 3. approach not suited for decision making
  applications
• decision making tends to be unstructured
• requirements change/uncertain so difficult to
  specify requirements

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II. Prototyping

• building an experimental system rapidly and
  inexpensively for users to evaluate
• working version of an IS or part of the system
• preliminary model

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Prototyping

• iterative process of development
• build preliminary design
• try it out
• refine it
• try it out etc.

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Prototyping

• prototyping much more iterative than SDLC
• promotes design changes
• less formal approach than SDLC
• quickly generate working model of system
• no detailed specifications

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Steps in prototyping

• 1. identify users basic requirements
• designer works with user only long enough to
  capture
• basic needs
• 2. develop working prototype
• designer creates prototype quickly

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Steps in prototyping

• 3. use prototype
• user works with prototype to determine how well
  it
• meets his/her needs
• user suggests improvements

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Steps in prototyping

• 4. revise and enhance prototype
• designer refines prototype based on users input
• repeat steps 3-4 until user satisfied

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Prototyping

• Approved prototype becomes basis for final
  specifications of the system
• more rapid, iterative and informal than SDLC

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Advantages of prototyping

• useful when uncertainty about information
  requirements or design solutions
• e.g. requirements for decision-oriented systems
  can be vague -- difficult to specify

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Advantages of prototyping

• good for design of user interface (part of system
  that end-users interact with)
• encourages user involvement throughout systems
  development

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Disadvantages of Prototyping

• should not substitute for careful requirements
  analysis
• better suited for smaller applications

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III. Application software packages

• develop a system by purchasing an application
  software package
• application software package - set of prewritten,
  precoded application software programs that are
  commercially available
• packages available for common functions such as
  payroll, accounts receivable, inventory control,
  etc.

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Choose packages when

• 1. functions common to many companies
• 2. information systems resources for in-house
  development in short supply
• 3. developing desktop applications for end-users

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Advantages of packages

• buying completed, working system
• require less internal resources - upgrades
  received from software supplier
• reduce bottlenecks in systems development

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Disadvantages of Packages

• can lack sophistication
• lack of integration of several functions
• may require customization - modify package to
  meet specific needs

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IV. Outsourcing

• hire external organization to build and/or
  operate systems
• can outsource all or some of systems function
• advantages and disadvantages

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Advantages of Outsourcing

• economy - less costly
• service quality - may get better service than
  from internal development
• predictability - outsourcing contract with fixed
  price
• flexibility - growth without making major changes
  in IT infrastructure

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Advantages of Outsourcing

• making fixed costs variable - pay only for amount
  of services used rather than for maintaining
  internal system
• freeing human resources for other projects
• freeing financial capital - can sell technology
  to vendor

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Disadvantages of Outsourcing

• loss of control over IS function
• vulnerability of strategic information - trade
  secrets, proprietary information
• dependency on viability of vender - i.e.
  financial, quality of services provided
• loss of knowledge and expertise